Apple's new 'Assembled in USA' iMac a bear to upgrade, repair • The Register
Memory Upgrades for iMac 21.5-Inch 2012 - Late 2013
I got a FREE 2013 iMac 21.5 with internal upgrades including Samsung evo ssd and 16gigs of ram. Then used open legacy patcher to install Mac OS Venture 13.5 beta. : r/osx
Apple iMac 2011 (Mid) 21.5-inch (iMac 11,2) SSD ,Ram & OSX Upgrades - ZD Laptop Service Centre
Memory Upgrades for iMac 21.5-Inch 2012 - Late 2013
iMac 21.5-inch Late 2013 – Full Tech Specs, Release Date, and Price
Final Words - 21.5-inch iMac (Late 2013) Review: Iris Pro Driving an Accurate Display